Load-lock apparatus and substrate cooling method

ABSTRACT

A load-lock apparatus includes a vessel arranged to change a pressure between a pressure corresponding to the vacuum chamber and the atmospheric pressure, a pressure adjusting mechanism which adjusts a pressure in the vessel to a pressure corresponding to the vacuum chamber and the atmospheric pressure, a cooling member having a cooling mechanism and arranged in the vessel to cool a substrate by having the substrate placed on or in proximity to the cooling member, a substrate deformation detection unit for detecting deformation of the substrate in the vessel, and a controller which reduces a cooling rate of the substrate when the substrate deformation is detected during a substrate cooling period until the vessel is adjusted to have the atmospheric pressure after the vessel is adjusted to have a pressure corresponding to the vacuum chamber and a high temperature substrate is loaded into the vessel from the vacuum chamber.

FIELD OF THE INVENTION

The present invention relates to a load-lock apparatus for use in avacuum processing unit which performs a vacuum process on a targetobject such as a semiconductor wafer, and a substrate cooling method foruse in the load-lock apparatus.

BACKGROUND OF THE INVENTION

In a manufacturing process of semiconductor devices, a vacuum processsuch as a film forming process and an etching process performed in avacuum atmosphere is widely carried out on a semiconductor wafer servingas a target substrate. Recently, a multi-chamber type vacuum processingsystem has been attracted attention from viewpoints of efficiency of thevacuum process and prevention of oxidation or contamination, wherein thesystem has a cluster tool type structure in which vacuum processingunits are connected to a transfer chamber maintained in a vacuum and awafer is transferred to each of the vacuum processing units by atransfer unit provided in the transfer chamber (see, e.g., JapanesePatent Application Publication No. 2000-208589).

In the multi-chamber type processing system, in order to transfer asemiconductor wafer from a wafer cassette disposed in the atmosphere tothe transfer chamber maintained in a vacuum, a load-lock chamber isprovided between the transfer chamber and the wafer cassette, and thesemiconductor wafer is transferred via the load-lock chamber.

When the multi-chamber type processing system is applied to a hightemperature process such as a film forming process, a semiconductorwafer serving as a target object having a high temperature of, e.g.,about 500° C. may be unloaded from the vacuum processing unit andtransferred to the load-lock chamber. However, when the wafer havingsuch a high temperature is exposed to the atmosphere, the wafer isoxidized. Further, when the wafer having such a high temperature isaccommodated in a receiving vessel, there is a problem that thereceiving vessel generally made of resin may be melted.

In order to avoid such problems, the wafer may be made to stand by untilits temperature reaches a temperature at which such problems do notoccur and, then, the wafer may be exposed to the atmosphere. In thiscase, however, a throughput is reduced. Accordingly, a cooling platehaving a cooling unit for cooling the wafer is provided in the load-lockchamber, so that the wafer is cooled by being placed on or in proximityto the cooling plate while the load-lock chamber in a vacuum state ispurged to have the atmospheric pressure.

In this case, if the semiconductor wafer is cooled rapidly, the wafermay be deformed due to a difference in thermal expansion between thefront and rear surface of the wafer W. Accordingly, a central or edgeportion of the semiconductor wafer is separated from the cooling plate,or the central and edge portions of the semiconductor wafer havedifferent distances to the cooling plate, thereby reducing coolingefficiency. Consequently, the cooling time becomes longer or thesemiconductor wafer still having a high temperature may be exposed tothe atmosphere.

In order to prevent the deformation of the semiconductor wafer, it isrequired to manage a pressure increasing rate when the load-lock chamberis adjusted to have the atmospheric pressure or a vertical position ofthe wafer when the semiconductor wafer is moved closer to the coolingplate. Accordingly, a proper purge recipe, which provides a goodcombination of the pressure increasing rate and the vertical position ofthe wafer, is created for each temperature of the wafer.

However, semiconductor wafers are differently deformed according totypes of films formed thereon. Further, there may exist a vast number oftypes of films according to users. Hence, it is very difficult to createan optimal purge recipe for each type of films. Accordingly, although apurge recipe corresponding to the temperature of the wafer is used, thesemiconductor wafer can be deformed depending on the type of film formedthereon.

SUMMARY OF THE INVENTION

Therefore, the present invention provides a load-lock apparatus capableof cooling a substrate at a practical cooling rate while preventingdeformation of the substrate to the maximum extent possible.

The present invention also provides a substrate cooling method for usein the load-lock apparatus to enable such a cooling of the substrate.

In accordance with a first aspect of the invention, there is provided aload-lock apparatus for use in transferring a substrate from theatmospheric atmosphere to a vacuum chamber maintained in a vacuum andtransferring a substrate having a high temperature from the vacuumchamber to the atmospheric atmosphere. The load-lock apparatus includes:a vessel arranged to change a pressure between a pressure correspondingto the vacuum chamber and the atmospheric pressure; a pressure adjustingmechanism which adjusts a pressure in the vessel to a pressurecorresponding to the vacuum chamber when the vessel communicates withthe vacuum chamber, and adjusts a pressure in the vessel to theatmospheric pressure when the vessel communicates with a space havingthe atmospheric atmosphere; a cooling member having a cooling mechanismand arranged in the vessel to cool a substrate by having the substrateplaced on or in proximity to the cooling member; and a substratedeformation detection unit for detecting deformation of the substrate inthe vessel. The load-lock apparatus further includes a controller whichreduces a cooling rate of the substrate when the substrate deformationdetection unit detects deformation of the substrate that is equal to orlarger than a predetermined value during a substrate cooling perioduntil the vessel is adjusted to have the atmospheric pressure after thevessel is adjusted to have a pressure corresponding to the vacuumchamber and the substrate having the high temperature is loaded into thevessel from the vacuum chamber.

In the load-lock apparatus, the controller may reduce the cooling rateby stopping increasing or reducing a pressure in the vessel when thesubstrate deformation detection unit detects the deformation of thesubstrate that is equal to or larger than the predetermined value whileincreasing the pressure in the vessel by the pressure adjustingmechanism.

The controller may resume an increase in pressure in the vessel when thesubstrate deformation detection unit detects that the deformation of thesubstrate becomes smaller than the predetermined value after thecontroller reduced the cooling rate.

The load-lock apparatus may further include wafer supporting pins whichare provided to be protruded from and retracted into the cooling member,receive the substrate while being protruded from the cooling member, anddescend with the substrate placed thereon such that the substrate isplaced on or in proximity to the cooling member. When the substratedeformation detection unit detects the deformation of the substrate thatis equal to or larger than the predetermined value, the controller mayreduce the cooling rate by raising the wafer supporting pins or stoppingdescending of the wafer supporting pins if the wafer supporting pinsdescend with the substrate placed thereon.

In the load-lock apparatus, when the substrate deformation detectionunit detects that the deformation of the substrate becomes smaller thanthe predetermined value after the controller reduced the cooling rate,the controller may restore the wafer supporting pins to their originalpositions or resumes descending of the wafer supporting pins if thedescending of the wafer supporting pins was stopped.

The substrate deformation detection unit may include a first sensor formeasuring a displacement of a central portion of the substrate and asecond sensor for measuring a displacement of an edge portion of thesubstrate, and may detect deformation of the substrate based on adifference between the detection value of the first sensor and thedetection value of the second sensor. The first sensor and the secondsensor may be laser displacement sensors.

The vacuum chamber may be a transfer chamber including a transfer unitfor transferring the substrate to a vacuum processing chamber thatperforms a high temperature process on the substrate in a vacuum, and ahigh temperature substrate is transferred to the vessel through thevacuum chamber after the high temperature process has been performed onthe substrate in the vacuum processing chamber.

In accordance with a second aspect of the invention, there is provided asubstrate cooling method for use in a load-lock apparatus for use intransferring a substrate from the atmospheric atmosphere to a vacuumchamber maintained in a vacuum and transferring a substrate having ahigh temperature from the vacuum chamber to the atmospheric atmosphere,the load-lock apparatus including a vessel arranged to change a pressurebetween a pressure corresponding to the vacuum chamber and theatmospheric pressure, a pressure adjusting mechanism which adjusts apressure in the vessel to a pressure corresponding to the vacuum chamberwhen the vessel communicates with the vacuum chamber, and adjusts apressure in the vessel to the atmospheric pressure when the vesselcommunicates with a space having the atmospheric atmosphere, and acooling member having a cooling mechanism and arranged in the vessel tocool a substrate by having the substrate placed on or in proximity tothe cooling member. The method may include: detecting deformation of thesubstrate in the vessel during a substrate cooling period until thevessel is adjusted to have the atmospheric pressure after the vessel isadjusted to have a pressure corresponding to the vacuum chamber and thesubstrate having the high temperature is loaded into the vessel from thevacuum chamber; and reducing a cooling rate of the substrate when thedeformation of the substrate that is equal to or larger than apredetermined value is detected.

In the cooling method, the cooling rate may be reduced by stoppingincreasing or reducing a pressure in the vessel when the deformation ofthe substrate that is equal to or larger than the predetermined value isdetected by the pressure adjusting mechanism while increasing thepressure in the vessel. An increase in pressure in the vessel may beresumed when it is detected that the deformation of the substratebecomes smaller than the predetermined value after the cooling rate wasreduced.

The load-lock apparatus may further include wafer supporting pins whichare provided to be protruded from and retracted into the cooling member,receive the substrate while being protruded from the cooling member, anddescend with the substrate placed thereon such that the substrate isplaced on or in proximity to the cooling member. When the deformation ofthe substrate that is equal to or larger than the predetermined value isdetected, the cooling rate may be reduced by raising the wafersupporting pins or stopping descending of the wafer supporting pins ifthe wafer supporting pins descend with the substrate placed thereon.When it is detected that the deformation of the substrate becomessmaller than the predetermined value after the cooling rate was reduced,the wafer supporting pins may be restored to their original positions ordescending of the wafer supporting pins is resumed if the descending ofthe wafer supporting pins was stopped.

In accordance with the present invention, after a high temperaturesubstrate is loaded into a vessel from a vacuum chamber, during asubstrate cooling period until the vessel is adjusted to have theatmospheric pressure, a substrate deformation detection unit detectsdeformation of a substrate. When deformation of a substrate that isequal to or larger than a predetermined value is detected, cooling ofthe substrate is modified to restore the deformed wafer to its originalstate. Thus, it is possible to cool a substrate at a practical coolingrate while preventing deformation of the substrate to the maximum extentpossible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view schematically showing a multi-chamber type vacuumprocessing system including a load-lock apparatus in accordance with anembodiment of the present invention.

FIG. 2 is a cross sectional view showing the load-lock apparatus inaccordance with the embodiment of the present invention.

FIG. 3 illustrates a state in which wafer supporting pins receives awafer in the load-lock apparatus of FIG. 2.

FIG. 4A explains one example of deformation of the wafer.

FIG. 4B explains another example of deformation of the wafer.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings. FIG. 1 is a transversal crosssectional view schematically showing a multi-chamber type vacuumprocessing system including a load-lock apparatus in accordance with anembodiment of the present invention.

The vacuum processing system includes four vacuum processing units 1, 2,3 and 4, each unit performing a high temperature process such as a filmforming process in a vacuum. The vacuum processing units 1, 2, 3 and 4are connected to four sides of a hexagonal transfer chamber 5,respectively. Further, load-lock apparatus 6 and 7 in accordance withthe embodiment of the present invention are connected to the other twosides of the transfer chamber 5, respectively. A loading/unloadingchamber 8 is connected to the load-lock apparatus 6 and 7 to be oppositeto the transfer chamber 5. Ports 9, 10 and 11, to which three FrontOpening Unified Pods (FOUPs) F capable of accommodating semiconductorwafers W serving as substrates to be processed are attached, areprovided at the side of the loading/unloading chamber 8 to be oppositeto the load-lock apparatus 6 and 7. Each of the vacuum processing units1, 2, 3 and 4 is configured to perform a specific vacuum process at ahigh temperature, e.g., a film forming process, on a target objectmounted on a processing plate placed therein.

As shown in FIG. 1, the vacuum processing units 1, 2, and 4 areconnected to the corresponding sides of the transfer chamber 5 via gatevalves G. Each of the vacuum processing units 1, 2, 3 and 4 is made tocommunicate with the transfer chamber 5 by opening the correspondinggate valve G, and is isolated from the transfer chamber 5 by closing thecorresponding gate valve G. Further, the load-lock apparatus 6 and 7 areconnected to the other two sides of the transfer chamber 5 via firstgate valves G1, and are connected to the loading/unloading chamber 8 viasecond gate valves G2. Further, each of the load-lock apparatus 6 and 7is made to communicate with the transfer chamber 5 by opening thecorresponding first gate valve G1, and is isolated from the transferchamber 5 by closing the corresponding first gate valve G1. Furthermore,each of the load-lock apparatus 6 and 7 is made to communicate with theloading/unloading chamber 8 by opening the corresponding second gatevalve G2, and is isolated from the loading/unloading chamber 8 byclosing the corresponding second gate valve G2.

The transfer chamber 5 includes a transfer unit 12 for loading/unloadingthe semiconductor wafers W into/from the vacuum processing units 1, 2, 3and 4 and load-lock apparatus 6 and 7. The transfer unit 12 is disposedat an approximately central portion of the transfer chamber 5. Thetransfer unit 12 includes two supporting arms 14 a and 14 b forsupporting the semiconductor wafers W. The two supporting arms 14 a and14 b are attached to a leading end of a rotatable andextensible/contractible portion 13 to be directed in oppositedirections. The transfer chamber 5 is maintained at a predeterminedvacuum level.

A shutter (not shown) is provided at each of the three ports 9, 10 and11 of the loading/unloading chamber 8, to which the FOUPs F capable ofaccommodating the wafers are attached. The FOUPs F accommodating thewafers or empty FOUPs F may be attached directly to the ports 9, 10 and11. When the FOUPs F are attached to the ports 9, 10 and 11, theshutters are opened such that the FOUPs F can communicate with theloading/unloading chamber 8 while preventing outside air from enteringthe loading/unloading chamber 8. Further, an alignment chamber 15 isprovided at one side of the loading/unloading chamber 8 to perform analignment of the semiconductor wafers W.

Further, the loading/unloading chamber 8 includes a transfer unit 16 forloading/unloading semiconductor wafers W into/from the FOUPs F and theload-lock apparatus 6 and 7. The transfer unit 16 has a multi-joint armstructure and is movable on a rail 18 in an arrangement direction of theFOUPs F. The semiconductor wafer W is transferred by the transfer unit16 while being loaded on a hand 17 provided at a leading end of thetransfer unit 16.

The vacuum processing system includes a process controller 20 having amicro processer (computer) for controlling each component of theprocessing system (e.g., the vacuum processing units 1 to 4, thetransfer chamber 5, the load-lock apparatus 6 and 7, and theloading/unloading chamber 8). Each component of the processing system isconnected to and controlled by the process controller 20. The processcontroller 20 is connected to a user interface 21 including a keyboardwith which an operator inputs commands to manage the vacuum processingsystem, a display for showing an operational status of the vacuumprocessing system, and the like.

The process controller 20 is also connected to a storage unit 22 whichstores control programs for implementing various processes in the vacuumprocessing system under the control of the process controller 20,programs for performing predetermined process in each component of thevacuum processing system under process conditions, e.g., a filmformation recipe for a film forming process, a transfer recipe for thetransfer of the wafer and a purge recipe for the pressure control of theload-lock apparatus, and the like. The recipes are stored in a storagemedium (not shown) of the storage unit 22. The storage medium may be afixed storage medium such as a hard disk, or a portable storage mediumsuch as a CD-ROM, a DVD and a flash memory. Further, the recipes may beproperly transmitted from another apparatus via, e.g., a dedicated line.

If necessary, a certain recipe may be retrieved from the storage unit 22in accordance with the commands inputted through the user interface 21and executed in the process controller 20 such that a desired process isperformed in the vacuum processing system under the control of theprocess controller 20. Further, the process controller 20 can controlthe pressure and/or the height of the wafer W in order to preventdeformation of the wafer W while a process is performed on the wafer Wbased on a standard purge recipe in the load-lock apparatus 6 or 7.

Next, the load-lock apparatus 6 and 7 in accordance with the embodimentof the present invention will be described in detail.

FIG. 2 is a cross sectional view showing the load-lock apparatus inaccordance with the embodiment of the present invention. Each of theload-lock apparatus 6 and 7 has a vessel 31 in which a cooling plate 32for cooling the wafer W placed thereon or disposed in proximity theretois supported by a leg portion 33.

At one sidewall of the vessel 31, there is provided an opening 34 toallow the vessel 31 to communicate with the transfer chamber 5maintained in a vacuum. At a sidewall of the vessel 31 opposite thereto,there is provided an opening to allow the vessel 31 to communicate withthe loading/unloading chamber 8 maintained at the atmospheric pressure.Further, the opening 34 can be opened and closed by the first gate valveG1, and the opening 35 can be opened and closed by the second gate valveG2.

A gas exhaust opening 36 for vacuum evacuating the vessel 31 and a purgegas inlet opening 37 for introducing a purge gas into the vessel 31 areprovided at a bottom portion of the vessel 31. The gas exhaust opening36 is connected to a gas exhaust line 41, and the gas exhaust line 41 isprovided with an opening/closing valve 42, an exhaust rate control valve43 and a vacuum pump 44. Further, the purge gas inlet opening 37 isconnected to a purge gas introduction line 45 for introducing a purgegas into the vessel 31. The purge gas introduction line 45 extends froma purge gas source 48 and is provided with an opening/closing valve 46and a flow control valve 47.

Further, when the wafer W is transferred to/from the transfer chamber 5maintained in a vacuum, the opening/closing valve 46 is closed and theopening/closing valve 42 is opened. Then, the vessel 31 is evacuated toa vacuum level corresponding to that of the transfer chamber 5 by thevacuum pump 44 via the gas exhaust opening 36 at a predetermined exhaustrate by adjusting the exhaust rate control valve 43. In this state, thefirst gate valve G1 is opened such that the vessel 31 communicates withthe transfer chamber 5.

Further, when the wafer W is transferred to/from the loading/unloadingchamber 8 maintained at the atmospheric pressure, the opening/closingvalve 42 is closed and the opening/closing valve 46 is opened. Then, apurge gas is introduced into the vessel 31 from the purge gas source 48via the purge gas introduction line 45 at, e.g., a predetermined flowrate by adjusting the flow control valve such that the vessel 31 has apressure close to the atmospheric pressure. In this state, the secondgate valve G2 is opened such that the vessel 31 communicates with theloading/unloading chamber 8.

Further, a method of introducing a purge gas may include supplying thepurge gas by using a brake filter (registered trademark) (not shown)formed of a porous ceramic at initial introduction stage and supplyingthe purge gas at a higher flow rate after the inner pressure of thevessel 31 reaches a predetermined level, in order to prevent particlesfrom swirling around, but it is not limited thereto.

The opening/closing valve 42, the exhaust rate control valve 43, theflow control valve 47 and the opening/closing valve 46 are controlled bya pressure adjusting mechanism 49 based on an inner pressure of thevessel 31 measured by a pressure gauge 63, so that the inner pressure ofthe vessel 31 can be changed between the atmospheric pressure and avacuum. The pressure adjusting mechanism 49 controls those valvesaccording to the instructions from the process controller 20.

Three wafer supporting pins 50 (only two pins are shown) fortransferring the wafer W are provided in the cooling plate 32 to beprotruded from the surface of the cooling plate 32 and retracted underthe surface of the cooling plate 32. The wafer supporting pins 50 arefixed on a supporting plate 51. Further, the wafer supporting pins 50are elevated via the supporting plate 51 as a rod 52 is elevated by adriving unit 53 such as a motor capable of controlling its verticalposition. Further, reference numeral 54 denotes a bellows.

A coolant flow path 55 is formed in the cooling plate 32. The coolantflow path 55 is connected to a coolant introduction line 56 and acoolant exhaust line 57. A coolant such as cooling water supplied from acoolant supply unit (not shown) is circulated in the cooling plate 32 tocool the mounted wafer W.

A ceiling wall 31 a of the vessel 31 is formed of a transparentmaterial, e.g., glass. Displacement sensors 61 and 62 are respectivelyprovided on the ceiling wall 31 a at positions corresponding to acentral and an edge portion of the wafer W. The two displacement sensors61 and 62 serve as a wafer deformation detection unit. The displacementsensors 61 and 62 have a function of measuring, e.g., a distance to thewafer W. The displacement sensors 61 and 62 are, e.g., laserdisplacement sensors.

The process controller 20 controls the load-lock apparatus 6 and 7, andalso controls the pressure adjusting mechanism 49 and the driving unit53 based on distance data transmitted from the displacement sensors 61and 62 so as to control an inner pressure of the vessel 31 and/or avertical position of the wafer W.

Next, an operation of the multi-chamber type vacuum processing systemwill be described focusing on the load-lock apparatus 6 and 7 inaccordance with the embodiment of the present invention.

First, a wafer W is unloaded from the FOUP F connected to aloading/unloading chamber 8 and loaded into the vessel 31 of a load-lockapparatus 6 (or 7). At this time, after the vessel 31 of the load-lockapparatus 6 is adjusted to have the atmospheric pressure, the secondgate valve G2 is opened and the wafer W is loaded into the vessel 31.

Thereafter, the vessel 31 is vacuum evacuated until the vessel 31 has apressure corresponding to that of the transfer chamber 5. The first gatevalve G1 is then opened, and the wafer W is unloaded from the vessel 31by the transfer unit 12. Then, the gate valve G of any one of the vacuumprocessing units 1, 2, 3 and 4 is opened and the wafer W is loaded intothe corresponding vacuum processing unit. A vacuum process, e.g., a filmforming process, is performed on the wafer W at a high temperature.

When the vacuum process is completed, the gate valve G is opened and thewafer W is unloaded from the corresponding vacuum processing unit by thetransfer unit 12. The first gate valve G1 of the load-lock apparatus 6or 7 is then opened and the wafer W is loaded into the correspondingvessel 31. While the wafer W is cooled by the coolant circulated in thecoolant flow path 55 of the cooling plate 32, the purge gas isintroduced into the vessel 31 such that the vessel 31 reaches theatmospheric pressure (wafer cooling period). Then, the second gate valveG2 is opened, and the process wafer W is accommodated in the FOUP F bythe transfer unit 16.

Further, the load-lock apparatus 6 may be used only for loading thewafers W into the processing system and the load-lock apparatus 7 may beused only for unloading the wafers W from the processing system.

An operation for the wafer cooling period after the wafer W that hasundergone the vacuum process is unloaded from the vacuum processing unitby the transfer unit 12 as described above will be described in detail.

The vessel 31 of one of the load-lock apparatus 6 and 7 is vacuumevacuated. The first gate valve G1 is then opened and the wafer W isloaded into the vessel 31. Subsequently, in a state where the wafersupporting pins 50 are protruded from the surface of the cooling plate32 as shown in FIG. 3, the wafer W is placed on the wafer supportingpins 50, and the first gate valve G1 is closed. Then, while a coolant iscirculated in the coolant flow path 55 of the cooling plate 32, thewafer supporting pins 50 are moved down such that the wafer W is placedon or in proximity to the cooling plate 32. A purge gas is introducedinto the vessel 31 at a predetermined flow rate such that an innerpressure of the vessel 31 is increased at a constant rate to theatmospheric pressure.

At the time when the wafer W is loaded into the vessel 31, the wafer Whas a high temperature of, e.g., 500° C. or more because the wafer w hasundergone a high temperature process such as a film forming process inone of the vacuum processing units 1 to 4. Accordingly, when the wafer Wis cooled down too rapidly, the wafer W is deformed as shown in FIG. 4Aor 4B due to a difference in thermal expansion between the front andrear surface of the wafer W.

Thus, first, while a purge gas is introduced into the vessel 31 at apredetermined flow rate based on a standard purge recipe, the wafer W iscooled by moving down the wafer supporting pins 50. At this time, thedisplacement of the wafer W is measured by the two displacement sensors61 and 62. If a minute deformation of the wafer W that is equal to orlarger than a predetermined value is detected, the cooling of the waferW is controlled to be slowed down. Specifically, a distance to the waferW measured by the displacement sensor 61 is compared with a distance tothe wafer W measured by the displacement sensor 62, and the cooling ofthe wafer W is controlled to be slowed down from a time point when thedifference between the distances to the wafer W is equal to or largerthan a predetermined value.

In this case, the deformation of the wafer W may occur during thedescending of the wafer W. Accordingly, the driving unit 53 needs to besynchronized with the displacement sensors 61 and 62 to obtain absolutevalues of the distances to the wafer W from the displacement sensors 61and 62.

The cooling rate (decreasing rate of the temperature) of the wafer Wincreases as an inner pressure of the vessel increases or/and the waferW becomes closer to the cooling plate 32. Accordingly, the cooling rateof the wafer W can be reduced by stopping an increase in the innerpressure of the vessel 31 by closing the opening/closing valve 46,moving up the wafer supporting pins 50, stopping the descending of thewafer W during the descending of the wafer W, or the like. Consequently,the minute deformation of the wafer W can be prevented by reducing thecooling rate as described above.

Further, the cooling rate of the wafer W can also be controlled to beslowed down by decreasing the inner pressure of the vessel 31 by vacuumevacuation, which makes the operation complicated.

If the displacement sensors 61 and 62 detect that the minute deformationbecomes smaller than the predetermined value by reducing the coolingrate as described above, the process controller 20 increases the coolingrate of the wafer W by opening the opening/closing valve 46 if theopening/closing valve 46 was closed, returning the wafer W to itsoriginal position by using the driving unit 53 if the wafer supportingpins 50 were moved up, or resuming the descending of the wafer W if thedescending of the wafer W was stopped during the descending of the waferW. Further, when the purge gas is introduced again by opening theopening/closing valve 46, the new flow rate of the purge gas may be setto be identical to or different from the previous flow rate.

Further, by performing those operations whenever a minute deformation ofthe wafer W that is equal to or larger than the predetermined value isdetected, it is possible to control the inner pressure of the vessel 31to become the atmospheric pressure while cooling the wafer W at apractical cooling rate without suffering from deformation whichinfluences cooling efficiency of the wafer W.

As described above, it is possible to achieve optimization of thecooling operation in the load-lock apparatus and to create, based on thesequence of operations, an optimal purge recipe which does not causedeformation exceeding an allowable value in a target wafer. Afterwards,a wafer, which has undergone the same process as the process performedon the target wafer in the vacuum processing unit, can be cooled basedon the created purge recipe. Further, such operation can be performed oneach of wafers having different types of films formed thereon.Accordingly, it is possible to create optimal purge recipes for wafershaving various films.

Further, errors in the cooling operation can be detected by thedisplacement sensors 61 and 62.

Further, as a conventional technique for preventing deformation of awafer during cooling of the wafer, there is proposed a method formeasuring an actual temperature of the wafer. In the temperaturemeasurement method, generally, a radiation thermometer is provided abovea ceiling wall of a processing vessel. In this case, the ceiling wallneeds to be formed of expensive special glass applicable to theradiation thermometer. However, in the present invention, there is noneed to directly measure the temperature of the wafer. Therefore, theceiling wall may be made of any material that allows a displacementsensor (e.g., a laser displacement sensor) to perform detection. Forexample, pyrex glass (registered trademark) that is inexpensive can beused as a material of the ceiling wall.

While the invention has been shown and described with respect to theembodiment, various changes and modification may be made without beinglimited thereto. For example, although the multi-chamber type vacuumprocessing system including four vacuum processing units and twoload-lock apparatus is employed in the above-described embodiment, thenumbers are not limited thereto. Further, the load-lock apparatus of thepresent invention can also be applied to a system including a singlevacuum processing unit without being limited to the multi-chamber typevacuum processing system. Further, although deformation of the wafer isdetected by using two displacement sensors in the above embodiment,another means such as a CCD camera may be used without being limitedthereto. Further, although deformation of the wafer that is equal to orlarger than a predetermined value is detected based on the differencebetween outputs of the displacement sensors in the above embodiment, itmay be detected based on a ratio of outputs of the displacement sensors.Further, a reducing means for the cooling rate is not limited to themeans described in the above embodiment. Further, a glass substrate forFPD or the like may be used as a target object without being limited tothe semiconductor wafer.

1. A load-lock apparatus for use in transferring a substrate from theatmospheric atmosphere to a vacuum chamber maintained in a vacuum andtransferring a substrate having a high temperature from the vacuumchamber to the atmospheric atmosphere, the load-lock apparatuscomprising: a vessel arranged to change a pressure between a pressurecorresponding to the vacuum chamber and the atmospheric pressure; apressure adjusting mechanism which adjusts a pressure in the vessel to apressure corresponding to the vacuum chamber when the vesselcommunicates with the vacuum chamber, and adjusts a pressure in thevessel to the atmospheric pressure when the vessel communicates with aspace having the atmospheric atmosphere; a cooling member having acooling mechanism and arranged in the vessel to cool a substrate byhaving the substrate placed on or in proximity to the cooling member; asubstrate deformation detection unit for detecting deformation of thesubstrate in the vessel; and a controller which reduces a cooling rateof the substrate when the substrate deformation detection unit detectsdeformation of the substrate that is equal to or larger than apredetermined value during a substrate cooling period until the vesselis adjusted to have the atmospheric pressure after the vessel isadjusted to have a pressure corresponding to the vacuum chamber and thesubstrate having the high temperature is loaded into the vessel from thevacuum chamber.
 2. The load-lock apparatus of claim 1, wherein thecontroller reduces the cooling rate by stopping increasing or reducing apressure in the vessel when the substrate deformation detection unitdetects the deformation of the substrate that is equal to or larger thanthe predetermined value while increasing the pressure in the vessel bythe pressure adjusting mechanism.
 3. The load-lock apparatus of claim 2,wherein the controller resumes an increase in pressure in the vesselwhen the substrate deformation detection unit detects that thedeformation of the substrate becomes smaller than the predeterminedvalue after the controller reduced the cooling rate.
 4. The load-lockapparatus of claim 1, further comprising: wafer supporting pins whichare provided to be protruded from and retracted into the cooling member,receive the substrate while being protruded from the cooling member, anddescend with the substrate placed thereon such that the substrate isplaced on or in proximity to the cooling member, wherein when thesubstrate deformation detection unit detects the deformation of thesubstrate that is equal to or larger than the predetermined value, thecontroller reduces the cooling rate by raising the wafer supporting pinsor stopping descending of the wafer supporting pins if the wafersupporting pins descend with the substrate placed thereon.
 5. Theload-lock apparatus of claim 4, wherein when the substrate deformationdetection unit detects that the deformation of the substrate becomessmaller than the predetermined value after the controller reduced thecooling rate, the controller restores the wafer supporting pins to theiroriginal positions or resumes descending of the wafer supporting pins ifthe descending of the wafer supporting pins was stopped.
 6. Theload-lock apparatus of claim 1, wherein the substrate deformationdetection unit includes a first sensor for measuring a displacement of acentral portion of the substrate and a second sensor for measuring adisplacement of an edge portion of the substrate, and detectsdeformation of the substrate based on a difference between the detectionvalue of the first sensor and the detection value of the second sensor.7. The load-lock apparatus of claim 6, wherein the first sensor and thesecond sensor are laser displacement sensors.
 8. The load-lock apparatusof claim 1, wherein the vacuum chamber is a transfer chamber including atransfer unit for transferring the substrate to a vacuum processingchamber that performs a high temperature process on the substrate in avacuum, and a high temperature substrate is transferred to the vesselthrough the vacuum chamber after the high temperature process has beenperformed on the substrate in the vacuum processing chamber.
 9. Asubstrate cooling method for use in a load-lock apparatus for use intransferring a substrate from the atmospheric atmosphere to a vacuumchamber maintained in a vacuum and transferring a substrate having ahigh temperature from the vacuum chamber to the atmospheric atmosphere,the load-lock apparatus including a vessel arranged to change a pressurebetween a pressure corresponding to the vacuum chamber and theatmospheric pressure, a pressure adjusting mechanism which adjusts apressure in the vessel to a pressure corresponding to the vacuum chamberwhen the vessel communicates with the vacuum chamber, and adjusts apressure in the vessel to the atmospheric pressure when the vesselcommunicates with a space having the atmospheric atmosphere, and acooling member having a cooling mechanism and arranged in the vessel tocool a substrate by having the substrate placed on or in proximity tothe cooling member, the method comprising: detecting deformation of thesubstrate in the vessel during a substrate cooling period until thevessel is adjusted to have the atmospheric pressure after the vessel isadjusted to have a pressure corresponding to the vacuum chamber and thesubstrate having the high temperature is loaded into the vessel from thevacuum chamber; and reducing a cooling rate of the substrate when thedeformation of the substrate that is equal to or larger than apredetermined value is detected.
 10. The method of claim 9, wherein thecooling rate is reduced by stopping increasing or reducing a pressure inthe vessel when the deformation of the substrate that is equal to orlarger than the predetermined value is detected by the pressureadjusting mechanism while increasing the pressure in the vessel.
 11. Themethod of claim 10, wherein an increase in pressure in the vessel isresumed when it is detected that the deformation of the substratebecomes smaller than the predetermined value after the cooling rate wasreduced.
 12. The method of claim 9, wherein the load-lock apparatusfurther includes wafer supporting pins which are provided to beprotruded from and retracted into the cooling member, receive thesubstrate while being protruded from the cooling member, and descendwith the substrate placed thereon such that the substrate is placed onor in proximity to the cooling member, and wherein when the deformationof the substrate that is equal to or larger than the predetermined valueis detected, the cooling rate is reduced by raising the wafer supportingpins or stopping descending of the wafer supporting pins if the wafersupporting pins descend with the substrate placed thereon.
 13. Themethod of claim 12, wherein when it is detected that the deformation ofthe substrate becomes smaller than the predetermined value after thecooling rate was reduced, the wafer supporting pins are restored totheir original positions or descending of the wafer supporting pins isresumed if the descending of the wafer supporting pins was stopped.